My guess is no HUD for model 3 until you first see them in S/X. S/X will probably get the HUD with the next refresh along with 2170 based packs.
There is definitely only one screen and Elon is being very coy as he could clearly shoot down a HUD if he wanted to. He has said enough about the car to date that are bigger issues then a HUD. For example, no P or D for the first cars built. No battery over 75 kWh will fit yet. Those are very large ticket items that have more real world impact on the car and he is very open about talking about them. Why not shoot down the HUD in the same way he has shot down a batter larger then 100 kWh in S/X and 75 kWh in the 3? My only guess is that a HUD is in the works, but will not be in the base Model 3 that comes out this year.
I had a very dumb idea and wanted to bounce it off this forum. What if the instrument panel was replaced by a cell phone docking station? You dock your cell when you get into the car and it acts like a 3D accelerated, 4G instrument panel. They could then do away with the 4G modem in the car to keep costs down (though I think they will still have 4G to gather autopilot data). Even in S/X the data is only covered for 3-4 years? In 3-4 years, with 5G coming, unlimited 4G plans will be as common as free text messaging.
I know it sounds dumb, but it will save a ton of money on the base model. As an option, they could have a 7" Samsung tablet that could be detached and used by passengers for entertainment or for the driver during fully autonomous driving. Tesla did just contract with Samsung for some mystery process, everyone thought it was a future replacement for nVidia Drive PX2, but maybe its just a basic tablet? Integrating this into the car would be drastically more simplistic then adding another fully integrated screen, because all you would need is USB and a cell phone app.
Thoughts?